The present invention relates generally to machines for receiving and processing articles, and more particularly, to a method and apparatus for positioning articles in such machines as the articles are conveyed. While the present invention is generally applicable to a variety of machines, it is particularly applicable to package wrapping machines wherein packages to be wrapped must be positioned at a particular location in a wrapping station to ensure that the packages are properly wrapped and do not jam the wrapping machines.
Article positioning within machines is commonly performed to permit standardized or automated operations to be carried out on the articles. For example, boxes, bottles, other containers or packages may be moved to a desired position for filling, labeling, wrapping or otherwise processing the article or its contents. In the prior art, a variety of article positioning arrangements have been utilized.
Articles can, of course, be positioned by hand; however, hand or manual positioning relies upon a machine operator and can result in reduced production and mispositioning which can jam or damage a machine. The simplest and most common mechanical arrangement is a plow or article guide angularly extending into a path along which articles must pass or be conveyed. In such article positioning arrangements, articles engage and slide along the guide until they reach a desired position defined by the guide. Usually, such guides are manually adjustable and must be set for a given article size or configuration.
Other prior art package positioning arrangements include active apparatus, such as rollers and cross-belts, which are used to carry packages in two mutually perpendicular directions to thereby convey packages to an alignment edge of a conveyor or other desired position. Alternatively, plows or package grippers may be dynamically operated by means of electrical, pneumatic or hydraulic solenoids such that they engage and force an article to a desired position. Dynamic positioning plows or package grippers are typically spring-loaded or otherwise resilient such that they are not likely to damage articles they are positioning.
In one article positioning application for a package elevating wrapping machine, packages must be substantially centered on an elevator for proper wrapping and to prevent interference and/or jams with remaining portions of the machine. Such a wrapping machine is disclosed in U.S. Pat. No. 4,505,092. In that patent, a combination package width sensing and centering arrangement comprises a pair of swing arms which are pivotally mounted on opposite sides of a package entryway. The swing arms are spring-biased to force the arms to angularly extend into the package entryway above its floor. The resiliency of the springs biasing the swing arms into the package entryway is sufficient to permit the arms to be deflected by entering packages to thereby sense the width of those packages, yet tends to center packages within the entryway of the machine. While this arrangement assists package positioning or centering within the machine to a limited extent, the initial positioning of packages by the operator is still essential to achieve proper machine operation and/or wrapping.
Manually adjustable plows do not provide the versatility required by an automatic machine, particularly one that is used to process a large variety of article sizes, since an operator would be required to repetitively adjust the positioning plows manually. While the mechanically operated positioning or centering devices can overcome the difficulty of the manually adjustable plows, they require motive and control apparatus which complicates and adds to the expense of machines including such devices. Further, since the balance of the springs and frictional mountings of the devices are not always perfect, article positioning tends to vary. Furthermore, if the spring-bias is set too high, lighter packages can be damaged; and, if it is set too high, heavier packages will override and defeat the positioning device.
It is, thus, apparent that the need exists for an accurate article positioning device which does not rely on complicated and expensive drive mechanisms, or spring-biasing, but provides a positive preferably mechanical arrangement for consistently and inexpensively positioning articles to be processed by a machine.